1. Field of the Invention
The present invention relates to a sputtering apparatus for manufacturing semiconductor devices and a sputtering method using the same, and more particularly, to a sputtering apparatus having a target backing plate equipped with a cooling line for cooling the target so as to achieve a good step coverage and a good deposition rate while depositing metal layers on wafers.
2. Background of the Related Art
Generally, one of the last steps in semiconductor device fabrication is forming a metal layer on a semiconductor substrate for pattern formation. The metal layer formation process is critical to production yield and the reliability of semiconductor devices, and is generally carried out by a sputtering method. The sputtering method provides easy control of the deposition rate for the metal layer, good surface characteristics, and selection from a wide variety of materials.
The sputtering process is carried out such that a reaction gas, e.g., argon gas (Ar), supplied inside a process chamber is turned into a plasma state, and positive ions of the reaction gas in the plasma state collide with a target so as to extract target atoms, which are deposited on the wafer.
FIG. 1 is a schematic diagram showing a conventional sputtering apparatus for manufacturing semiconductor devices, which comprises a process chamber 10 in which a sputtering process is carried out in a vacuum state by operation of a vacuum pump (not shown). A stage 16 is located in a lower portion of the inside of a process chamber 10, and the stage 16 serves as an anode on which a wafer 18 to be processed is mounted. In the upper portion of the process chamber 10, opposite the stage 16, there is provided a target 12 which serves as a cathode.
In addition, a backing plate 14 is provided on the back side of the target 12, and a cooling water line (not shown) is provided inside the backing plate 14 for supplying cooling water to control the temperature of the target 12. One end of the cooling water line is connected to a cooling water supply source 24 via a cooling water supply line 22, and the other end of the cooling water line is connected to a cooling water discharge line 23. The cooling water supplied from the cooling water supply source 24 passes through the cooling water supply line 22, and is supplied to the cooling water line so as to cool the target 12 coupled with the backing plate 14, and is thereafter discharged.
A high frequency power source 26 is connected to the target 12, which forms an electric field between the stage 16 and the target 12. On one side of the process chamber 10, there is provided a gas supply line 20 for supplying a reaction gas, such as argon gas (Ar), into the process chamber 10.
Therefore, after locating a wafer 18 on the stage 16 inside the process chamber 10 where a specific vacuum state is formed by operating a vacuum pump (not shown), reaction gas is supplied into the process chamber 10 through the gas supply line 20.
Then, on receipt of 10 kW to 12 kW from the power source 26, an electric field is formed between the target 12 and the stage 16, and the reaction gas supplied into the process chamber 10 is accelerated by the electric field and turned into the plasma state. The positive ions of the reaction gas in the plasma state move toward the target 12 which functions as a negative electrode, and collide with the target 12 so as to extract target atoms from the target 12. The extracted atoms from the target 12 are deposited on the wafer 18.
The repeated collisions between the positive ions of the reaction gas in the plasma state and the target 12 generate heat, and the heat from the target 12 is removed by the cooling water passing through the cooling water line of the backing plate 14 coupled with the target 12, after which it is discharged into the cooling water discharge line 23.
However, with the high-integration of multi-layered semiconductor devices, contact sizes are becoming smaller, and their depths are becoming deeper, so that the step coverage of the metal layer deposited on the wafer is becoming more difficult. Attempts have been made to improve the step coverage, such as the installation of a collimator between the target and the wafer, and controlling the inner pressure of the process chamber.
However, installing a collimator between the target and the wafer causes a problem in that the target material is filtered at the collimator so that the deposition rate of target atoms deposited on the wafer is decreased. In addition, particles generated from the target atoms deposited on the collimator contaminate the wafer during subsequent processes. Therefore, an improved sputtering apparatus and sputtering method are needed to improve both the step coverage of metal layers deposited on the wafer and the deposition rate.